1. Field of the Invention
The present invention relates to a liquid ejection apparatus that ejects liquid from a recording head and, in particular, to a liquid ejection apparatus that supplies liquid from a liquid container holding the liquid to a recording head through a supply tube.
2. Description of the Related Art
There is an ink jet recording apparatus that ejects liquid from a recording head to record information on a recording medium.
Japanese Patent Laid-Open No. 2005-66520 describes a recording apparatus that supplies pigment ink from an ink pack fixed to the main body of the printer to a recording head through an ink supply tube and ejects the pigment ink from the recording head to record information on a recording sheet. This patent document also describes the prevention of settlement of pigment particles within the ink pack by up-and-down movements of a stirring element provided in the ink pack.
This patent document also describes arranging a semiconductor strain-gage pressure transducer as an ink end sensor in an ink flow path from the ink pack to the recording head. The ink flow path is sealed to the atmosphere, and when the ink pack becomes empty of ink, a negative pressure in the ink flow path increases. Sensing the absence of ink in the ink pack by detecting the increase in negative pressure is described in the above-mentioned patent document.
However, with the configuration described in the above-mentioned patent document, if the ink supply tube is cut or anomaly occurs, such as the occurrence of a crack, the ink end sensor does not detect a negative pressure. Thus when anomaly occurs in the ink supply tube, a negative pressure is not formed in the ink supply tube, and the ink end sensor does not function. Additionally, because there is no configuration for detecting anomaly in the ink supply tube, when anomaly occurs in the ink supply tube, a problem arises in that ink leaks in the printer.
The apparatus described in the above-mentioned patent document does not have a configuration for detecting whether a stirring element normally operates. Therefore, when anomaly occurs in the operation of the stirring element, the density of ink supplied from the ink pack is not uniform. This may cause a problem in that the recording head poorly ejects ink or the image quality degrades.